Spectrometry systems can be used to confirm the presence of or to determine the concentration, electronic or magnetic properties, or local chemical environment of a given chemical species in a sample, such as in physical or analytical chemistry. Two common spectroscopy methods are absorption spectrometry and fluorescence spectrometry. In absorption spectrometry, a beam of light is sent through a sample to be analyzed, and certain wavelengths of the light are absorbed by the sample. By comparing the wavelengths of the absorbed light to known chemical absorption spectra, the components of the sample may be identified. In fluorescence spectrometry, a sample is bombarded by high energy light or other radiation capable of inducing electronic transitions to higher energy levels. As the excited electrons fall back to lower energy levels, the wavelength of the emitted light can be used to identify numerous atomic-scale properties of the sample.
The Rowland circle and either the Johann or Johannson geometries can be employed in spectrometry systems. In this arrangement, a curved, crystal-based (e.g., silicon or germanium) diffraction element is used for wavelength-specific focusing of X-rays. For applications involving higher-energy X-rays, a radius of curvature of one meter or more is typically required. This in turn creates a large working distance (which is a function of the radius of curvature) that results in a poor collection solid angle and creates the need for precision tolerances with little margin for error during fabrication, calibration, and operations. Further, every time such a device is moved, it must be calibrated to these tolerances, meaning that use of these devices can be expensive and time consuming. Similar considerations apply to the von Hamos geometry, which makes use of a simpler cylindrical design with only partial focusing properties.